https://wccftech.com/microsoft-releases-windows-10-2004-build-19041-21-to-the-slow-ring/

The Windows maker has today released a cumulative update to the upcoming Windows 10 version 2004 (from the 20H1 branch) that is currently being tested by the Insiders in the Slow ring.

Version 2004 is expected to be delivered to the public in Spring even though there were reports that we will see the RTM build coming in December, 2019. Since that didn't happen, it is likely that Microsoft is following the same schedule that it has for the previous Spring editions of its desktop operating system.